Production of bulked yarns



' T. W. TARKINGTON ET AL April 22, 1969 Filed Feb. 7, 1964 Sheet w -w a y 2 2 J 0- y E L 0 m m I C T E E T F. N G L N E I AE m K G OWN m KG ,0 NN -06 G S N lllllll -0 s I N F I R R 0 0 R 0 H 0 F c 0 I C s 8% S N ,v -0 0 G 6 6 v Q I Q 0 e 0 IO C Q V Q N V H 4 Q I 4 v I X WL Q 1 Q 3 I O O 0 O O 0 Q 2 I O 2 I 0 OF CYCLE FIG. 2.

INGTON R. MARTIN April 22, 1969 Sheet Filed Feb. 7, 1964 T E N 6 AE M K6 M r M R Cs I 0 zbo % 0F CYCLE N 0.02 mw zE:m &

FIG.3.

IO CONSTANT SHRINKAGE RANGE o 20 40 so OF CYCLE FIG. 4.

INVENTORS M WIN/LAM NW N MA m M T T A WM YM H m 2, 1969 1'. W.TARK|NGTON ETAL I 3,439,490

PRODUCTION OF BULKED YARNS Filed Feb. 7, 1964 Sheet 3 of s w WILLIAM R. MARTIN .ATTO

United States Patent US. Cl. 57-140 2 Claims ABSTRACT OF THE DISCLOSURE This invention relates to novel composite yarns and to fabrics prepared from such yarns. More particularly, this invention relates to a method of making composite yarns which are voluminous or bulky in character and dimensionally stable and are formed from synthetic filaments having variable shrinkage characteristics which cause the yarn to bulk upon being subjected to shrinking conditions.

It is well known that yarns produced from staple fibers, especially from the natural fibers such as wool and cotton, are inherently more voluminous and bulky in character than are continuous filament yarns. The bulkiness of the staple yarns imparts to a fabric made from such a yarn a soft hand and high covering power. Various methods have been employed in an attempt to prepare bulked yarns from the synthetic filaments which have the desirable properties possessed by the natural fibers.

Heretofore, one method used in the production of bulked yarns from man-made fibers is a normal high-bulk process. This is accomplished by blending regular fibers with a lower percentage of high-bulk fibers to form a composite yarn. The resulting yarn is bulked by developing the shrinkage of the high-bulk portion thereof with the aid of heat. This may be achieved in a heated chambet, a hot water bath, a dye bath by steaming, or other heat treatment. A composite yarn produced by this process has the undesirable property of what is commonly called a locust wing" appearance, which is obviously objectionable. Such an appearance is imposed by the fact that the relaxed high-bulk fibers accede to the center of the yarn to form a core thereby giving the regular fibers a radially staggered appearance when viewed transversely of the mean longitudinal axis of the yarn.

While a composite bulked yarn having a more uniform appearance can be made by blending together fibers with varying shrinkage properties, this resulting yarn has the undesirable property of being unstable when placed under tension, and particularly under hot-wet conditions encountered during the dyeing of this type yarn, or in the washing of fabrics and textile articles containing such yarn. This problem is emphasized by the fact that a yarn known commercially as a Space or A to Z yarn is spontaneously extensible to the extent of up to approximately 30% of its length due to tension applied thereto by its own weight during some of the known conditions of dyeing. The desirable uniform appearance of this type yarn is made possible by the differential shrinkage of the individual filaments comprising the composite yarn. The dimensional unstability of such yarn exists because in each segment thereof the longer filaments which provide the bulking effect remain free of tension while the shorter filaments support the load imposed on the yarn. When yarns of this type are placed under tension the individual filaments which become the load-bearing memiCC bers either break or stretch lengthwise successively until the desirable yarn structure is destroyed. Accordingly, the primary object of this invention is to overcome the disadvantages described herein above by providing a novel composite yarn having both desirable bulk and hand characteristics while being dimensionally stable.

Another object of the present invention is to provide a novel dimensionally stable composite yarn that can be woven or knitted into a fabric either before or after permanent bulking of the yarns has been developed.

Other objects of the present invention will be apparent to those skilled in the art from the following more detailed description.

In accordance with the present invention there is provided a method of producing a high-bulk yarn from tows or filaments prepared from fiber-forming thermoplastic polymers and copolymers comprising heating such tow or filament while stretching, or alternately relaxing, the tows or filaments to impart thereto predetermined ranges of both variable and constant shrinkages in the longitudinal direction thereof. The variable shrinkage segment of a given length of tow or filaments processed in accordance with the aforesaid method preferably constitutes 50 to percent of the length treated in one cycle and the remaining part of the composite yarn is comprised of filaments occurring in the constant shrinkage portion of the cycle. A cycle is herein defined as the amount of stretch or relaxation applied to a given length of tow or filaments from minimum to maximum, or vice versa, to a point where the stretch or relaxation changes direction thereby repeating the cycle. The differential between minimum and maximum is determined by the amount of stretching or relaxing imposed upon the tows or filaments during heating whereby a predetermined shrinkage range is established. A range of shrinkage is defined as shrinkage differential imparted to the several segments which make up the given length of tow or filaments processed during a cycle. In this instance, after blending the fiber produced during one cycle or recurring cycles into a composite yarn, the components thereof are comprised of a given number of filaments of which 50 to 80 percent of such filaments have differential shrinkage values ranging from a preferred minimum to a preferred maximum, and the remainder of the filaments have like shrinkage characteristics at the preferred maximum whereby the bulked yarn is rendered dimensionally stable. 'Under some conditions, however, the variable shrinkage part of the cycle may be from 30 to percent of the entire cycle and the remaining 70 to 5 percent thereof at constant shrinkage, depending upon the degree of dimensional stability desired. It will be understood that the constant shrinkage components become the load-bearing members when a load is imposed on the bulked composite yarn. Accordingly, an increase in the proportion of constant shrinkage fibers forming the composite yarn similarly increases the number of load-bearing members whereby the dimensional stability of the novel bulked yarn and the wear resistance of fabric formed therefrom is improved.

The fiber employed in this invention may be prepared from any synthetic fiber-forming materials such as polyacrylonitrile, copolymers, including binary and ternary polymers containing at least 80 percent by weight of acrylonitrile in the polymer molecule, or a blend comprising polyacrylonitrile with from 2 to 50 percent by weight of another polymeric material, the blend having an overall polymerized acrylonitrile content of at least 80 percent by weight. For example, the polymer from which the fibers are prepared may be a copolymer of from 80 to 98 percent by weight of acrylonitrile and from 2 to 20 percent by weight of another monomer containing the linkage and copolymerizable with acrylonitrile. Suitable monoolefinic monomers include acrylic, alpha-chloroacrylic and methacrylic acid; the acrylates, such as methylmethacrylate, ethylmethacrylate, butylrnethacrylate, methoxymethyl methacrylate, beta-chloroethyl methacrylate, and the corresponding esters of acrylic and alpha-chloroacrylic acids; vinyl chloride, vinyl fluoride, vinyl bromide, vinylidene chloride, l-chloro-l-bromoethylene; methacrylonitrile; acrylamide and methacrylamide; alpha-chloroacrylamide, or monoalkyl substitution products thereof; methylvinyl ketone; vinyl carboxylates, such as vinyl acetate, vinyl chloroacetate, vinyl propionate, and vinyl stearate; N-vinylirnides, such as N-vinylphthalimide and N-vinyl-succinimide; methylene malonic esters; itaconic acid and itaconic esters; N-vinylcarbazole; vinyl furane; alkyl vinyl esters; vinyl sulphonic acid; ethylene alpha,beta-dicarboxylic acids or their anhydrides or derivatives, such as diethylcitraconate and diethylmesaconate, styrene, vinyl naphthalene, vinyl-substituted tertiary heterocyclic amines, such as the vinylpyridines and alkyl-substituted vinylpyridines, for example, 2-vinylpyridine, 4-vinylpyridine and 2-methyl-5-vinylpyridine; l-vinylimidazole and alkyl-substituted l-vinylimidazoles, such as 2, 4, or S-methyl-l-vinylimidazole.

The polymer may be a ternary polymer or higher interpolymer, for example products obtained from the interpolymerization of acrylonitrile and two or more of any of the monomers, other than acrylonitrile enumerated above. More specifically, and preferably the ternary polymer comprises acrylonitrile, methacrylonitrile and 2- vinylpyridine. The ternary polymers preferably contain from 80 to 98 percent by weight of acryonitrile, from 1 to percent by weight of a vinyl-pyridine or a l-vinylimidazole, and from 1 to 18 percent by weight of another substance, such as methacrylonitrile or vinyl chloride.

The polymer may also be a blend of a polyacrylonitrile or of a binary interpolymer of from 80 to 98 percent by Weight of acrylonitrile and from 1 to 20 percent by weight of at least one other containing substance with from 2 to 50 percent of the weight of the blend of a copolymer of from 10 to 70 percent by weight of acrylonitrile and from 30 to 90 percent by weight of at least one other containing polymerizable monomer. Preferably, when the polymeric material comprises a blend it will be a blend of a copolymer of 90 to 98 percent acrylonitrile and from 2 to 10 percent of another mono-olefinic monomer, such as a vinyl acetate, which is not receptive to dyestuff, with a sufiicient amount of a copolymer of from 10 to 70 percent of acrylonitrile and from 30 to 90 percent of a vinyl-substituted tertiary heterocyclic amine, such as vinylpyridine or l-vinylimidazole, to give a dyeable blend having an overall vinyl-substituted tertiary heterocyclic amine content of from 2 to 10 percent, based on the weight of the blend.

The fiber may be prepared from other synthetic fiberforming materials as, for example, polyethylene terephthalate, polyamides, as, for example, polyhexamethylene adipamide, polyhexamethylene sebacamide, polycaproamide and copolymers of various amides, vinyl polymers, as, for example, vinyl chloride/vinyl acetate copolymers,- polymers and copolymers of tetrafluorethylene, monochloro-trifluorethylene and hexafluoropropylene, polyethylene, cellulose derivatives, as, for example, cellulose acetate, regenerated cellulose, or ethyl cellulose.

In accomplishing the objects of this invention, several methods, hereafter described, may be employed to prepare the fibers having the necessary shrinkage characteristics which are required for blending purposes to form the novel composite yarn described herein. The invention will be more readily understood by reference to the drawings wherein:

FIGURE 1 illustrates graphically the percent shrinkage versus percent of cycle wherein the variable portion of the processing cycle is linear;

FIGURE 2 is similar to FIGURE 1, but illustrates the variable portion of the processing cycle as being nonlinear;

FIGURE 3 is the same as FIGURE 2 except the nonlinearity of the variable portion of the processing cycle is reversed;

FIGURE 4 is similar to FIGURE 1, but illustrates the variable portion of the processing cycle occurring intermediate constant portions thereof;

FIGURE 5 is a side view of the invention, greatly enlarged, showing a segment of the blended fibers prior to bulking;

FIGURE 6 is a side view of the invention, greatly enlarged, showing a segment of the blended fibers after bulking which form a dimensionally stable bulked yarn having a substantially uniform surface appearance;

FIGURE 7 is a side view of a common high-bulk blended yarn illustrating the non-uniform surface possessed by yarns of this type.

FIGURES 1-4 illustrate graphically the percent shrinkage at degrees centigrade plotted as ordinate versus percentage of fiber processed at selected intervals during any given cycle. In referring to FIGURE 1 it will be apparent that a yarn blended from fiber prepared in accordance with the cycle illustrated, approximately 35 percent of the blend will exhibit 20 percent shrinkage properties when bulked and the remainder of the blend will exhibit variable shrinkage which varies linearly from 20 percent to substantially no shrinkage. Obviously, the shorter fibers form the core and the variable length fibers spiral outwardly around the core yarns progressively to form a bulked yarn having a uniform cross section. Since 35 percent of the blend becomes load-bearing members upon imposition of tension thereon, the yarn is thereby rendered dimensionally stable. As illustrated by the several figures, one skilled in the art can make various blends whereby a desired yarn can be prepared in a particular instance. For example, the dimensional stability or amount of bulk may be varied by merely changing the processing cycle. FIGURES 2 and 3 are referred to for the purpose of illustrating such an example. In a yarn blended from fiber prepared in accordance with FIGURE 2, the nonlinear condition would tend to increase dimensional stability and slightly decrease bulk, whereas, the reversed nonlinear condition shown in FIGURE 3 produces an opposite eifect. Yet another type yarn having different characteristics can be formed from fiber processsed in accordance with FIGURE 4. Here the yarn would tend to be more porous because of the additional percentage of non shrinkage fiber whereby bulkiness of the yarn is increased.

By Way of example, a yarn in accordance with the invention is produced from a high-bulk tow consisting of fibers of polyacrylonitrile, the tow having a uniform shrinkage of 22 percent when immersed in boiling water or like heating. The tow is subjected to treatment over live steam in a discontinuous manner to relax the tow and to impart to the tow longitudinally thereof a complete range of variable and constant shrinkage cycles which will have the configuration graphically illustrated in FIGURES 1-4 of the accompanying drawings, wherein the percentage values of shrinkage of the tow at 100 degrees centigrade are plotted against the percentage values of the variable shrinkage ranges in the cycles being illustrated by dotted lines 10 and the constant shrinkage ranges by continuous lines 11. In this example 65 percent of the tow has completely variable shrinkage after treatment which shrinkage varies from to 20 percent. The remaining 35 percent of the tow is at a constant shrinkage of 20 percent which is constant at the maximum shrinkage of the variable shrinkage range. Other typical examples within the scope of the invention are set out in the following table:

Shrinkage of Variable Variable Constant Constant tow before shrinkage, shrinkage shrinkage, shrinkage, treatment percent range, percent percent of cycle percent of cycle The high-bulk tow used as a starting material in the examples (a), (b), (c) and (f) set out in the above table, is comprised of filaments having like stretch characteristics at the percent indicated. Such tow is treated during a predetermined cycle successively wherein a relaxation process occurs to provide the variable and constant shrinkage portions and their respective shrinkage range. If a stretch process is used, distinguished from a relaxation process, tows having less than 5 percent shrinkage, such as those indicated under (d) and (e) in the above table, should be used. The example indicated under (f) is illustrated by FIGURE 4.

Three methods are described herein for processing tow in accordance with the invention. One method involves relaxing a tow or filament having a degree of shrinkage in excess of the required maximum shrinkage. The relaxing at operation is performed on a special apparatus by feeding the tow or filament through a relaxing zone at a variable speed corresponding to the shrinkage cycle desired to insure that only sufiicient relaxation is permitted to obtain the maximum shrinkage percentage. The feed of the apparatus is then increased through a range of shrinkage by passing from the maximum speed thereof, gradually reducing the speed to the desired minimum which is maintained throughout the remainder of the treatment cycle for producing the constant shrinkage portion of the tow or filament.

A second method of producing the fiber contemplates imparting to a tow or continuous filament a variable stretch having a stretch cycle which increases from zero to the maximum desired during a predetermined portion of the cycle, the tow or filament then being maintained at the maximum stretch for the remaining part of the cycle. An example of such a cycle is illustrated by the curves appearing in FIGURES 1-4 of the accompanying drawings. The length of the cycle will depend partially on the amount of blending that the fiber may receive in subsequent processing steps such as during carding and drawing operations. It will be understood by those skilled in the art that the cycle can be extended substantially with an increase in the amount of subsequent blending.

According to a third method of producing the required fiber to be used in carrying out this invention, there is employed a fiber of completely variable shrinkage having blended therewith a high-bulk fiber having the same shrinkage as the maximum shrinkage possessed by the variable shrinkage blend. For example, 35 percent of the component fiber used for preparing the novel composite yarn is a high-bulk acrylonitrile polymer staple having 20 percent shrinkage is blended with 65 percent acrylonitrile polymer tow of variable shrinkage and having a shrinkage range of 0 to 20 percent to form a dimensionally stable yarn.

Other alternatives such as maintaining constant feed while varying the takeup, and differential lengthening of the relaxation period while maintaining constant feed and take-up speeds may be utilized in the production of the fibers described herein. Both of these alternatives may be employed with the relaxation and stretch methods.

The material produced in accordance wtih the present invention would normally be in the form of a continuous filament and subsequently reduced to staple form prior to being blended into a yarn. The reduction to staple form can be accomplished an any desired manner by conventional apparatus to suit the blending process. Staple can be blended on any conventional staple-to-yarn processing system such as linen, cotton, woolen, worsted or jute systems, or fed as tow blends into tow-to-yarn conversion systems such as the Pacific Converter.

Referring to FIGURE 5, a longitudinal section is shown of an unbulked yarn 12 comprised of a plurality of fibers 13 which are processed and blended in accordance with the above methods. Prior to development of the bulkiness' retained by blended fibers 13, the fibers are oriented in a side by side relationship with respect to the mean longitudinal direction thereof. When fibers 13 are heated to develop the shrinkage characteristics possessed by such yarns, a novel dimensionally stable bulked yarn 14 is produced, shown in FIGURE 6. The fibers having maximum shrinkage characteristics, when heated, form the core of the composite yarn while remaining fibers of the blend, which are characterized by variable shrinkage propensities, tend to spiral outwardly in coils around the core fibers with varying amplitude corresponding to the shrinkage of the individual fibers. The core yarns provide increased stability in the yarn to overcome the destruction of yarn structure experienced heretofore in the known yarns having similar surface appearance. There are known bulked yarns of similar stability, however, these yarns are comprised of high-bulk fibers which form the core when heated and regular low shrinkage fibers. A yarn of this type is illustrated by FIGURE 7. The low shrinkage fibers 15 tangle outwardly from the core fibers 16 to form a bulky yarn 17 having an uneven surface appearance, commonly referred to as a locust wing appearance.

The present invention offers many advantages over the prior art. Yarns produced in accordance with this invention afford greater strength duringv dyeing and hot-wet processing than the known yarns of like bulk and hand. Such yarns also possess a more desirable structure than conventional high-bulk yarns, and are dimensionally stable in both yarn form and fabric made from such yarn. Finally, a yarn possessing excellent aesthetic properties and soft hand can be provided since blends of various denier per filament fibers exhibit these additional properties. These desirable properties can be enhanced by the fact that the load-bearing fibers have constant shrinkage characteristics whereupon stronger fiber can be utilized in this part of the blend to reduce the number of such members normally required to prepare a dimensionally stable yarn and maximize the bulk. Fiber strength is controlled by denier, chemical composition, or prior processing thereof and may be increased by either of these means.

We claim:

1. A method of making high bulk yarn from synthetic filaments comprising (a) imparting a constant shrinkage characteristic to a first length of said filament to form a first component having a constant shrinkage characteristic along the length thereof,

(b) imparting a variable shrinkage characteristic to a second length of said filament to form a second component having a shrinkage characteristic which varies along the length of said second component, the maximum shrinkage characteristic of the second component being no greater than the shrinkage characteristic of the first component,

(c) blending the first and second components to form a yarn, and

(d) subjecting the yarn to a source of heat to shrink the filaments in the yarn.

2. A high bulk yarn comprising first and second distinct components of filaments, said first component of filaments each having a constant shrinkage characteristic along the length thereof, said second component of filaments having a shrinkage characteristic which varies uniformly along the length of said filaments, the maximum shrinkage characteristic of each of the filaments of the second component being no greater than the shrinkage characteristic of the filaments of the first component.

References Cited UNITED STATES PATENTS 5/1966 Hitomi et 'al 2872 2/1967 Ruddell et al. 57157 US. Cl. X.R. 2872; 57-157 U.S. DEPARTMENT OF COMMERCE PATENT OFFICE Washington, D.C. 20231 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,439,490 April 22, 19b! Terry Wesley Tarkington et a1.

It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:

Column 5, in the table, fifth column, line 4 thereof, "2" should read Signed and sealed this 14th day of April 1970.

(SEAL) Attest:

Edward M. Fletcher, Jr. WILLIAM E. SCHUYLER, JR.

Attesting Officer Commissioner of Patents 

